W. Riedl in Chemische Berichte, 85, 692 (1952) described the synthesis of humulon and lupulone compounds which had been known to exist in nature and which had further been known to possess certain antibiotic properties. In this publication he reported the synthesis of humulon by diprenylation of the disodium salt of phlorisovalerophenone yielding as a byproduct (9%--see compound XV on page 701) 3-phenyl phlorisovalerophenone. In this publication, W. Riedl also reported that, during the synthesis of 4-desoxy humulon, a byproduct was obtained which was speculated to comprise a chroman or benzodipyran. However, the structure hereof was not further examined nor reported, although this byproduct exhibited certain antibacterial activity.
F. Bohlman and various co-workers in a number of publications have reported the extraction of various compounds (mainly in the form of mixtures) from certain Helicrysum plant species, which compounds were postulated to have the 3-alkenyl phlorophenone structure. Certain related chromans were also extracted or prepared from compounds extracted from the plant material. However, as far as the inventors of the present invention are aware, no antimicrobial properties of these compounds have been reported.
V. K. Ahluwalia and various co-workers in Synthesis, 526 and 527, (1981) reported the synthesis of chromans and dichromans, both classes of compounds being derived from the corresponding phlorophenone compound. Although the aforementioned types of compounds are known to have certain physiological activities, for example including antioxidant, tranquillizing, and antidepressant properties and properties relating to fertility, it appears as if no antimicrobial properties of these compounds have been reported (see reference number 2 in the first-mentioned paper by Ahluwalia et al).
Other workers are known to have prepared phlorophenones, chromans, and dihydrobenzofurans, for example, A. Robertson and T. S. Subramanian, J. Chem. Soc., 286 (1937) and 1545 (1937); R. A. Finnegan et al, Tetrahedron Letters, 13, 11 (1959); E. D. Burling et al, Tetrahedron, 21, 2653 (1965); P. W. Austin et al, Tetrahedron, 24, 3247 (1968); R. H/a/ nsel et al, Phytochem, 19, 639 (1980). Likewise, however, as far as the inventors of the present invention are aware, no antimicrobial activity or properties of these compounds have been reported.
It has long been known that phenols and chlorinated phenols exhibit bactericidal action. Phenol itself, the simplest member of the series was already introduced as an antiseptic during the nineteenth century. It has been shown that the more highly substituted phenol derivatives are more selective in their action than the simpler phenols, and some of the more highly substituted phenol derivatives also exhibit antifungal activity. The more selective phenols are used mostly for skin disinfections, whilst the less refined members are used as general disinfectants, for instance in the disinfection of floors, drains, and stables for example. Phenols are also used as preservatives in pharmaceutical preparations.